In a wireless telecommunications system, mobile devices such as wireless user equipment traverse a wireless coverage area while communicating with other hosts that are either inside the wireless domain or outside in a wired domain. Any host, wired or wireless, that uses the Internet Protocol (IP) for communication is assigned an IP address that can be used to uniquely distinguish that host from all others. In a wired network environment, the IP address assigned to a host has topological significance, meaning that the address can be used to locate the point where the host is physically attached to the network. Routers, which are responsible for forwarding packets to a host, use the address to find a routing table entry that defines the next hop along the path to the attachment point associated with the address used by that host. Since information in routing tables is quasi-static, routers assume that an attachment point and its corresponding host are immobile. Therefore, only a change in network topology (e.g., a change caused by link failures) will cause a change in the routing information.
In contrast, the IP address assigned to a mobile device operating in a wireless telecommunications system will likely not be related to the point were the device is attached to the network. This is especially true when a mobile device communicates with different access points (e.g., base stations) as it travels through a wireless domain. More particularly, it is not uncommon in today's heterogeneous wireless environment for a multi-homed mobile device to have simultaneous connections to multiple access networks, each of which may use a different radio access technology. When this is the case, a unique IP address is assigned to the mobile device by each access network. However, no generic mechanism currently exists within current Internet protocols to correlate those individual IP addresses to the same mobile device. Instead, each assigned address represents a different end-point from the routing perspective of the Internet at-large.
This lack of correlation becomes problematic during an intersystem or inter-technology handover when a mobile device attempts to move packet flows from one radio access network to another. Such packet flows are used when the information requested by the mobile device is too large to fit into a single datagram. When this is the case, the requested information is segmented across multiple datagrams either by the source of the information (e.g. a web or cache server) or by an intermediate transit point (e.g. a wireless gateway). As a result, datagrams in the packet flow may arrive at the mobile device in any order or may even be lost in transit, especially if the mobile device changes its point(s) of attachment to the network.